This invention relates to a self-propelled harvesting machine, such as a combine or the like, and more particularly to a harvesting machine having a forward header that is adapted to remove crop material from a field as the machine advances, leaving a relatively short upright crop stubble in the field. Such a header is shown in U.S. Pat. No. 3,982,384, also assigned to the assignee herein. The row crop header that is shown in said patent includes a plurality of independent row units that are mounted on the header frame for independent vertical floating adjustment, so that the row units are free to follow the contour of the ground. Each row unit includes a fore and aft passage adapted to receive a row of crop material as the machine advances, a cutting apparatus adapted to sever the crop from the field relatively close to the ground as it moves rearwardly along the passage and a conveyor for conveying the severed crop rearwardly along the passage to a crop converging auger that feeds crop material rearwardly through a feeder housing to a crop treating mechanism in the combine. the weight of each row unit is partially counterbalanced by a spring and the rest of the weight is supported on the ground by a pair of ground-engaging shoes that slide along the ground on opposite sides of each row.
While with the forward drive wheels of the combine preferably run between the rows, with certain size combines and with certain row spacings it is necessary that one or both of the drive wheels drive on top of a row, rolling over the stubble left in the row. With the trend for narrower row spacings and larger high floatation tires, the possibility of avoiding running on a row is reduced.
One of the features of the row crop header shown in said U.S. Pat. No. 3,982,384 is the ability of the individual row units to sever the crop in each row very close to the ground, which, in the case of crops such as soybeans, is highly desirable to reduce harvest losses. However, the relatively short crop stubble stands upright and when the drive wheels roll over the short upright stubble, which in many cases is quite rigid, the stubble penetrates the tire, rather than being deflected or bent over by the rolling tire as it would be in the case of a longer stubble. While the stubble does not puncture the tire, the numerous penetrations into the tire thread causes rapid wear of the tire. As is well known, the large tires on modern combines or the like are very expensive, so that the accelerated tire wear significantly increases the cost of operating the machine.